metacity assert failure: metacity:ERROR:core/bell.c:211:bell_flash_window_frame: assertion failed: (window->frame != NULL)

Binary package hint: metacity

no idea what caused this to happen. but metacity crashes pretty often for me. (at least once a day, i imagine.)

ProblemType: Crash
Architecture: i386
AssertionMessage: metacity:ERROR:core/bell.c:211:bell_flash_window_frame: assertion failed: (window->frame != NULL)
CrashCounter: 1
Date: Mon Sep 21 19:10:55 2009
DistroRelease: Ubuntu 9.10
ExecutablePath: /usr/bin/metacity
NonfreeKernelModules: nvidia
Package: metacity 1:2.27.1-0ubuntu1
ProcCmdline: /usr/bin/metacity
ProcEnviron:
 PATH=(custom, user)
 LANG=en_US.UTF-8
 SHELL=/bin/bash
ProcVersionSignature: Ubuntu 2.6.31-9.29-generic
Signal: 6
SourcePackage: metacity
StacktraceTop:
 raise () from /lib/libc.so.6
 abort () from /lib/libc.so.6
 g_assertion_message () from /usr/lib/libglib-2.0.so.0
 g_assertion_message_expr () from /usr/lib/libglib-2.0.so.0
 ?? ()
Title: metacity assert failure: metacity:ERROR:core/bell.c:211:bell_flash_window_frame: assertion failed: (window->frame != NULL)
Uname: Linux 2.6.31-9-generic i686
UserGroups: adm admin cdrom dialout lpadmin plugdev sambashare